Cellulose nitrate coating compositions



Feb. 21, 1950 2,498,091

W. K. MOFFETT CELLIILOSE NITRATE COATING COMPOSITIONS Filed June 14, 1947 I007, MONOMER COMPOSITION K E Y ol-IDS COMPOSITION) ABCDEF OPERATIVE AREA GHIJKL PREFERRED AREA EXAMPLE I EXAMPLE 2 EXAMPLE 3 EXAMPLE 40nd? EXAMPLE 5 EXAMPLE 6 QQLbO N- I001, PLASTIOIZER OELLULOSE NITRATEIOO Q JNVENTOR.

WALTER K. MOFFETT ATTORNEY Patented Feb. 21, 1950 CELLULOSE NITRATE COATING COMPOSITIONS Walter K. Moflett, Flint, Mich., asslgnor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Application June 14, 1947, Serial No. 754,727

This invention relates to improved high solids coating compositions and, more particularly, to high solids coating compositions formulated with low viscosity cellulose nitrate and a polymerizable bifunctional monomer composition to yield useful finishes for metallic and non-metallic substrata.

Heretofore, finishes from high solids lacquers and enamels formulated with low viscosity cellulose nitrate have lacked the desired combination of toughness, mar-proofness, ease of rubbing, good cold crack resistance and good outdoor durability. Another unfavorable feature of commercial high solids, low viscosity cellulose nitrate finishes is poor resistance to solvent attack. Heretofore the plasticizing and resinous modifiers for the cellulose nitrate in the lacquer have been 11 Claims. (01. zsq-un either non-polymerizable materials, polymers wherein polymerization is substantially complete before admixing with the cellulose nitrate, or polymerizable monofunctional monomers rather than bifunctional monomers which polymerize readily to an insoluble state.

These shortcomings limit the use of the previous high solids, low viscosity cellulose nitrate coating compositions to applications where the finish is normally subject to a limited range of temperature variation and where it will not be subjected to marring, scratching, or solvent attack.

This invention has an object the provision of coating compositions which contain exceptionally high percentages of film-forming materials at normal spraying consistency.

Another object is the provision of high solids,

low viscosity cellulose nitrate coating compositions which yield finishes that are unaffected when subjected to wide temperature Variations, and particularly to low temperatures.

A further object is the provision of high solids, low viscosity cellulose nitrate coating compositions which yield finishes having high resistance to attack by solvents in common household use.

A still further object is the provision of high solids, low viscosity cellulose nitrate coating compositions which yield finishes that are resistant to scratching and other types of marring.

Still another object is the provision of a lacquer finish which is print-free and ready for further finishing operations without passing through the green stage characteristic of orthodox finishes, thereby permitting economical accelerat on of the finishing operations.

Other objects will be apparent as the description proceeds.

These objects are accomplished by combining low viscosity cellulose nitrate with polymerizable bifunctional glycol methacrylate monomer compositions and plasticizing modifiers.

The polymerizable bifunctional glycol methacrylate monomer compositions may be prepared by the esterification of methacrylic acid with a glycol or a mixture of glycols, or by mixing together the preformed esters of methacrylic acid and a glycol or a. mixture of glycols. The copending application of Anderson and Ramler, Serial-No. 671,395, filed May 21, 1946, fully describes the production ofmonomer compositions by the esterification of methacrylic acid with a mixture of glycols.

In the drawing, the single figure is a triangular graph showing the operative and preferred ranges (based on solids content) of the three ingredients. The area delineated by points ABCDEF shows that the low viscosity cellulose nitrate may range from approximately 8% to 45%, the polymerizable bifunctional methacrylate monomer composition from approximately 42% to 89%, and the plasticizing modifiers from 0.5% to 25%. The points GHIJKL delineate applicants preferred ranges; i. e., the low viscosity cellulose nitrate from approximately 13% to 38%, the

polymerizable bifunctional methacrylate monomer composition from approximately 48% to 79%, and the plasticizing modifiers from 5% to 20%.

The following examples are illustrative of the preferred embodiments of my invention, the ingredients of each composition being shown as percent by weight:

EXAMPLE 1 Clear lacquer I Per cent The coating composition of this example contains 45% solids at spraying viscosity shown as follows:

Per cent Cellulose nitrate 35 Monomer composition A 55 Alkyd resin A l0 Monomer composition A is a mixture of dlmethacrylate esters of polyethylene glycol 200, the latter being a mixture of various glycols, which mixture has a weighted average molecular weight oi 200x15; i. e., between 185 and 215. An

analysis of a typical mixture is as follows:

Average Weight Material Molecular Per Cent Weight y gf g 2.78, Monoethylene glycol 62 5.6 Diethylene g1 col 106 i8. 47 Triethylene g ycol.-. 150 18. l Telraethylcne glycol 194 205. 5 I2. 25 Pentaetllylene glycol. 238 4. 6 Hexaetliylene glycol 282 Alkyd resin solution A is a castor oil modified glyceryl phthalate of 55% oil length, cut to 60% solids in a mixture of 90 parts of high solvency petroleum lacquer diluent and 10 parts of butyl alcohol.

Alkyd resin solution B is a linseed oil modified glycerol phthalate of 53% oil length, cut to 55% solids in high solvency petroleum naphtha.

EXAMPIE 3 Clear lacquer Per cent Cellulose nitrate (18-23 centipoises) 11.1 Ethyl alcohol (denatured) 7.0 Monomer composition A 33.3 Alkyd resin solution A 9.3 Methyl ethyl ketone 15.1 Ethyl acetate 7.0 Butyl acetate 7.0 Anhydrous isopropyl alcohol 10.0 Cobalt nitrate 0.1 Benzoyl peroxide 0.1

EXAMPLE 4 Clear lacquer I I Per cent Cellulose nitrate (18-23 centipoises) 8.7 Ethyl alcohol (denatured) 4.7 Monomer composition B 40.8 Alkyd resin solution C 7.9 Butyl acetate 2.0 Methyl ethyl ketone 15.1 Methyl isobutyl ketone 4.0 Acetone 10.0 Toluene 6.3 Cobalt nitrate hexahydrate 0.3 Benzoyl peroxide 0.2

4 Monomer composition B is a mixture of equal parts of the monomeric di'methacrylate esters of polyethylene glycol 200 and the monomeric dimethacrylate ester of diethylene glycol, the weighted average molecular weight or the glycols being 153.

Alkyd resin solution C is a cottonseed oil modifled glyceryl phthalate resin of oil length, cut to 70% solids in toluene.

EXAMPLE 5 Clear lacquer Per cent Cellulose nitrate (18-23 centipoises) 7.0 Ethyl alcohol (denatured) 3.8 Monomer composition C 56.0 Alkyd resin solution D 11.8 Butyl acetate 2.0 Amyl acetat 1.7 Methyl ethyl ketone 7.0 Methyl isobutyl ketone 2.1 Toluene 8.2 Cobalt nitrate 0.2 Benzoyl peroxide 0.2

Monomer composition C is a mixture of equal parts of the monomeric dimethacrylate esters of polyethylene glycol 400 and the monomeric dimethacrylate ester of diethylene glycol, the weighted average molecular weight of the glycols being 253.

Alkyd resin solution D is a hydrogenated castor oil modified glyceryl phthalate resin of 45% oil length, cut to solids in toluene.

EXAIVIPIE 6 Clear lacquer Per cent Cellulose nitrate (18-23 centipoises) 12.0 Ethyl alcohol (denatured) 6.5 Monomer composition A 33.0 Alkyd resin solution E 7.7 Anhydrous isopropyl alcohol 3.0 Methyl ethyl ketone 15.0 Acetone 15.0 Butyl acetate 4.0 Toluene 3.5 Cobalt nitrate hexahydrate 0.2 Benzoyl peroxide 0.1

Alkyd resin solution E is a coconut oil acid modified ethylene glycol-pentaerythritol-phthalic anhydride alkyd resin cut to solids in toluene. The solids of the said resin have the essential components in the following proportions:

Per cent Coconut oil acids 46.3 Ethylene glycol 7.3 Pentaerythritol 16.0 Phthalic anhydride 30.4

The compositions of Examples 2, 3, 4, 5, and 6 are of the same general type as that oi Example 1, but have a lower content of cellulose nitrate and a higher proportion of polymerizable monomeric material. and exhibit a consistency normal for spray application without further reduction.

EXAMPLE 7 Pigmented lacquer Per cent Cellulose nitrate (18-23 centipoises) 7.5 Ethyl alcohol (denatured) 4.1 Butyl acetate 9.0 Titanium dioxide 9.5 Monomer composition A 34.0 Butyl alcohol 2.0 Methyl ethel ketone 20.0 Toluene 6.9 Alkyd resin solution F 6.5 Cobalt nitrate hexahydrate 0.3 Benzoyl peroxide 0.2

,acrylate monomer composition may be used in the practice of this invention, such as mixtures of preformed glycol esters of methacrylic acid or glycol esters derived from the methacrylic acid esterification of a glycol or mixtures of glycols having the empirical formula wherein n is an integer, usually varying from 1 to 20 for mixtures, and the molecular weight of the glycol in the case of a single species or the weighted average molecular weight of the glycols in the case of a mixture is in the range of about 100 to 300. The value of 11. may exceed 20 with the provision that the preferred limitation on weighted average molecular weight in the range of about 100 to 300 for the glycol mixture is maintained. Methacrylate monomers derived from glycol mixtures with a weighted average molecular weight in excess of 300 yield polymers lacking in strength and toughness, thereby defeating an object of this invention. Mixtures of glycols with a weighted average molecular weight of approximately 100 yield brittle methacrylate polymers which alone are considered as of little commercial value because of brittleness, but within the scope of this invention they are useful in combination with low viscosity cellulose nitrate and plasticizing alkyd resins.

Applicants preferred polymerizable bifunctional methacrylate monomer composition is the mixture of dimethacrylate esters of polyethylene glycol 200, the latter being a mixture of various glycols, which mixture has a weighted average molecular weight of 200: 15.

They contain 40-70% solid-s Conventional lacquer plasticizers may be used in the practice of the present invention within the limitation of compatibility with the combination of cellulose nitrate and methacrylate. Likewise, orthodox lacquer plasticizers may be used in combination with alkyd resins. However, applicant prefers the oil modified alkyd resins as the plasticizing ingredient of the composition because they may be used in larger quantities before the plasticizing efiect is undesirably high for the methacrylate monomer.

Plasticizing oil modified alkyd resins other than those shown in the examples may be used. Different oil lengths and different modifying oils and oil acids of the non-drying, semi-drying, and drying types, such as soya bean or perilla, in addition to those shown in the examples, as well as different alkyd resins, may be used. However, since the main purpose of the alkyd is its plasticizing action, the'long oil length, soft alkyds are preferred. 1

The volatile constituents of these high solids formulations are orthodox lacquer solvents and diluents. However, it is preferred to use a major proportion of solvents and diluents having a faster evaporation rate than normal butyl acetate to avoid solvent or diluent entrapment in the polymerizing coating. Aromatic hydrocarbons are preferred to aliphatic hydrocarbons.

In formulating cellulose nitrate compositions, it is within the scope of this invention to use 12.5- parts by weight of polymerizable methacrylate monomer composition to 10 parts by weight of cellulose nitrate. Applicant prefers to use 15-50 parts of monomer composition to 10 parts of cellulose nitrate.

Finishes containing 0.5% to 25% plasticizer, based on the weight of the vehicle solids, accomplish theobjects of this invention. It is preferred, however, to limit the plasticizer content to the approximate range of about 5% to about 20% By comparison. previous cellulose nitrate compositions formulated for high solids application rely on a high ratio of plasticizing alkyd resin to cellulose nitrate, and the alkyd is generally a short oil length, drying oil modified resin. Unrubbed finishes range fromabout 15 to 50 parts of alkyd for 10 parts of cellulose nitrate by weight. These finishes depend on oxidation of the modifying oil for the development of adequate hardness, and lack the desirable features contributed by the compositions of this invention.

Prior rubbed finishes vary widely in composition depending on the type of application and the quality required. In general, these are formulated with non-drying oil modified alkyds, hard resins, and orthodox lacquer plasticizers in combination with cellulose nitrate, the resinplasticizer mixture ranging from about 5 to 15 parts for 10 parts of cellulose nitrate. These compositions do not yield high solids at spraying consistency because of the high content of cellulose nitrate which is the main contributor to the viscosity of the product Polymerizabl monomeric methacrylates generthat polymerization may proceed at a rate suitable to the type of application. The use of inorganic salts of cobalt to provide a rapid polymerization cycle is described in Marks U. S. application Serial No. 688,977, filed October 25, 1946.

Pigmented enamels, such as that shown in Example 7, may be prepared by first dispersing the pigment in a cellulose nitrate vehicle, or in the plasticizing resin vehicle, by methods known to the art. In addition to color efi'ects, extender pigments may be used for flatting a clear vehicle. It is preferred that the pigments and fiatting agents be of such chemical character that they do not unduly affect the polymerization.

Clear or pigmented lacquers of this invention, containing exceptionally high solids (about 40% to 70%), may be sprayed. One coat application yields a film thickness in the range of approximately 1.5 to 3.0 mils when subjected to a temperature range from 65 F. to 270 F., preferably 120 F. to 215 F., the film build per coat depending on the solids content of the lacquer, the rate of solvent loss between the spray gun and the work, and the rate of polymerization of the wet finish. Higher film builds may be obtained 7 by multiple coat application, but the second coat must be applied before the monomeric material of the first coat has been substantially polymerized in order to obtain adequate adhesion. However,

two coat applications would be abnormal inasmuch as the film thickness obtained by one coat application is generally considered adequate. Three or four coats are required to obtain a comparable film thickness with previous low viscosity cellulose nitrate lacquers.

Once the monomeric methacrylate composition has polymerized, the film is no longer attacked by the volatile constituents of the parent lacquer.

Heretofore, lacquers formulated with 18-23 centipoise viscosity cellulose nitrate were generally characterized by inferior cold cracking resistance, but the present finishes overcome this due to the resulting polymer.

The compositions of this invention may be applied to wooden objects by spraying, without special spray equipment, and yield useful and decorative, tough, and mar resistant finishes of exceptionally high film build, e. g., 2 mils, in one coat. Metal objects may be similarly finished by application of these finishes over conventional undercoat systems.

These finishes, when aged for two weeks at 120 F. and then subjected to cyclic temperature variations of 10 F. to 120 F., show an extremely high resistance to checking or cold cracking without sacrificing the other outstanding properties discussed herein. Hitherto it was not possible to achieve this high resistance to checking or cold cracking except at a sacrifice in other desirable properties, I

These finishes also possess outstanding print resistance and hardness upon the completion of the polymerization cycle, and do so without passing through the conventional green stage, thus eliminating delays in finishing operations.

The finishes of this invention resist attack by alcohol, nail polish removers, lacquer thinners, and similar liquids that attack previous lacquer finishes. This property, in conjunction with mar and scratch resistance, makes these finishes particularly useful for protective and decorative applications on tables, desks, trays, and similar objects where such abuses are common. These resistant finishes showa further improvement over previous lacquers in that the finished objects may be subjected to outdoor exposure and wide variations in temperature without rapid deterioration of the finish. In addition, these coating compositions are characterized by unusually high solids at spraying viscosity which results in economy of application.

It is apparent that many widely different embodirnents of this invention can be made without departing from the spirit and scope thereof; and, therefore, it is not intended to be limited except as indicated in the appended claims.

I claim:

1. A sprayable, high solids coating composition in which the solids content comprises 8-45% of 10-40 centipoise cellulose nitrate, 42-89% of polymerizable dimethacrylate esters of a mixture of glycols each having the formula wherein n is an integer, the weighted average molecular weight of the glycol mixture being between and 300, and 05-25% of a compatible 5. The coating composition of claim 1, in which the plasticizer is an oil modified alkyd resin.

6. The coating composition of claim 1, in which the plasticizer is a 55% castor oil modified glyceryl phthalate resin.

'7. A sprayable, high solids coating composition in which the solids content comprises 13-38% of 10-40 centipoise cellulose nitrate, 48-79% of polymerizable dimethocrylate esters of a mixture of glycols each having the formula Hmon -CHM) or wherein n is an integer, the weighted average molecular weight of the glycol mixture being between 100 and 300, and 5-20% of a compatible plasticizer.

8. A sprayable, high solids coating composition in which the solids content comprises 23-45% of 18-23 centipoise cellulose nitrate, 42-89% of polymerizable dimethacrylate esters of a mixture of glycols each having the formula HO (CH2CH2O) 11H wherein n is an integer, the weighted average molecular weight of the glycol mixture being between 100 and 300, 05-25% of a compatible plasticizer, and a pigment.

9. A sprayable, high solids coating composition,

in which the solids content comprises 8-45% of 18-23 centipoise cellulose nitrate, 42-89% of polymerizable dimethacrylate esters of a mixture of glycols each having the formula wherein n is an integer, the weighted average molecular weight of the glycol mixture being between 100 and 300, 05-25% of a compatible plasticizer, and a polymerization accelerator.

10. A sprayable, high: solids coating composition containing the following ingredients:

Per cent Cellulose nitrate (18-23 centlpoises) 11.1

Ethyl alcohol (denatured) 7.0 Dlmethacrylate esters of polyethylene glycol 55% castor oil modified glyceryl phthalate solution (60% solids) 9.3 Methyl ethyl ketone 15.1 Ethyl acetate 7.0 Butyl acetate 7.0 Anhydrous isopropyl alcohol 10.0 Cobalt nitrate 0.1 Benzoyl peroxide 0.1

11. A sprayable, high solids coating composition containing the following ingredients:

Per cent Cellulose nitrate (18-23 centipoises) 15.7 Ethyl alcohol (denatured) 9.7

Dimethacrylate esters of polyethylene glycol I Percent 55% castor oil modified glycerylphthalate:

solution (60% solids) 7.5 Cobalt nitrate hexahydrate 0.1 Benzoyl peroxide 0.1 Methyl ethylketone 42.1

WALTER K. om'rr.

anrnnnncas orrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,783,168 Bruson Nov. 25, 1930 2,064,802 Edgar Dec. 15, 1936 2,155,590 Garvey Apr. 25, 1939 2,156,144 Bruson Apr. 25, 1939 2,160,532 Barrett et a1 May 30, 1939 2,379,246 Muskat June 26, 1945 2,402,942 Bludworth July 2, 1946 2,420,720 Pechukas et al May 20, 1947 Certificate of Correction Patent No. 2,498,091 February 21, 1950 WALTER K. MOFFETT It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 8, line 43, for dimethoerylate read dimethaorylate;

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 16th day of May, A. D. 1950;

THOMAS F. MURPHY,

Assistant G'ommfiaiom of Patents.

Certificate of Correction Patent No. 2,498,091 February 21, 1950 WALTER K. MOFFETT It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 5, line 45, for that portion of the formula reading HO, read (7H,; column 8, line 43, for dimethocrylate read dimethacrylate;

THOMAS F. MURPHY,

Asaz'atant C'ommz'ssz'oner of Patents. 

8. A SPRAYABLE, HIGH SOLIDS COATING COMPOSITION IN WHICH THE SOLIDS CONTENT COMPRISES 8-45% OF 18-23 CENTIPOISE CELLULOSE NITRATE, 42-89% OF POLYMERIZABLE DIMETHACRYLATE ESTERS OF A MIXTURE OF GLYCOLS EACH HAVING THE FORMULA 